Recent back-end upgrades by Microsoft to Office 365's SharePoint Online are causing problems for some users and developers whose workflows and applications have been disrupted by a variety of bugs.

At SP Marketplace, a Sacramento, California, developer of business applications that run on SharePoint, staffers are now constantly monitoring their software in case Microsoft back-end changes break functionality in their products.

Meanwhile, ObjectSharp, a Toronto provider of Microsoft software development, consulting and training, had to scramble late last month to troubleshoot a problem for one of its customers that was also linked to SharePoint Online upgrades.

Other users and developers are voicing similar complaints and concerns in discussion forums, blogs, Twitter and other social media channels.

The problems highlight the perils of using or building applications for hosted software: vendors can change the code and inadvertently affect the functionality for some users and developers.

Microsoft acknowledged that it has been making changes recently to the SharePoint Online back end in Office 365, and it listed the bugs triggered by the updates in a knowledge base support note. It is pruning the list as issues get solved.

According to Microsoft, it recently did a service update for the SharePoint Online version based on the 2010 edition of the product. It has also started to gradually upgrade SharePoint Online customers from the 2010 edition over to the new 2013 edition, which hasn't been officially released but is due to ship "early" this year.

The note with the list of bugs addresses issues caused by both the service update and by the move from the 2010 to the 2013 edition of SharePoint, Microsoft said in a statement.

It also said that it is motoring through the issues, fixing almost half of them "within the first few days." And it maintained that the problems are neither widespread nor systemic.

"We, too, have updated numerous processes in our service update methodology to avoid events in the future," the emailed statement reads.

The problems included design changes between the 2010 and 2013 editions, while others were "isolated customers' configuration issues."

However, Microsoft also acknowledged it has spent "a large amount of resources to improve the service update" and it paused its roll out "until all possible fixes were in place."

In addition, the company plans to publish a "comprehensive blog post" this week as well as reach out to SharePoint Online administrators to "help mitigate known changes and articulate required steps to prepare."

Office 365 customers that are moved to the 2013 edition of SharePoint Online are being put in what Microsoft calls "14 mode", which means that the customers don't get access to any new 2013 features or user interface changes. These customers are running on top of SharePoint 2013 but won't have access to the new features until the product officially ships, according to the company.

Meanwhile, SP Marketplace has been having to regularly tweak its applications for SharePoint Online since around November, and it now views Office 365 as a problematic platform for its software, said CEO Darrell Trimble.

"We have to check every day to make sure everything is running okay, and we have also asked our customers to tell us if something isn't running well," he said. "The minute we learn something has changed, we push out an update. We've been proactive."

Ironically, SP Marketplace isn't having this issue with third-party hosting companies of the stand-alone SharePoint Online, because they typically don't change their version of the software often, and when they do, they give advance notice and details about what they'll change.

The issue SP Marketplace is having is with the SharePoint Online instances that run within the broader Office 365 suite, which is hosted exclusively by Microsoft.

"I don't know if the issue is that Microsoft doesn't understand that people are relying on that platform and on its features and functions to do what they have to do," Trimble said.

Right now, it seems to Trimble that Office 365's SharePoint Online "isn't really in the 2010 edition nor in the 2013 edition -- it's somewhere in between," and that's a big problem for SP Marketplace, which started building applications for SharePoint on-premise versions about two years ago, and modified them for SharePoint Online about a year ago.

"When you're trying to run applications or build things on top of that, it's a little hard to do because it becomes an unstable environment," Trimble said.

It's also a problem for SP Marketplace's customers, since the applications are for core business processes.

"We had very few issues until Microsoft started to talk about the 2013 upgrade and started to change things in SharePoint Online under the covers," he said.

SP Marketplace tested its applications against the first preview version of SharePoint Online 2013 that Microsoft made available, and they worked fine, but they have been breaking as Microsoft has further modified the software, he said.

It doesn't seem like a good decision to update Office 365's SharePoint Online with the "14 mode" code of SharePoint 2013 if that edition hasn't shipped officially yet, he said.

"Being a good Microsoft partner, I'll do anything I can to help Microsoft, but it seems they're shooting themselves in the foot," Trimble said.

At ObjectSharp, a pilot SharePoint site built for one of its customers disappeared from end users' views in late December, sending ObjectSharp on a frantic, two-day troubleshooting mission.

At first, ObjectSharp's staff didn't suspect the culprit could be a Microsoft back-end upgrade, so it spent a big chunk of time trying to isolate the problem on its customer's end.

A 45-minute call to Microsoft support yielded no helpful clues, but on a second call a different Microsoft representative suggested the problem was likely related to the back-end upgrades.

Sure enough, when Object Sharp checked, their customer's SharePoint Online version had been moved to the "14 mode" version.

"But the user interface is still the 2010 interface," said Bruce Johnson, ObjectSharp's vice president of technology.

Neither ObjectSharp nor its customer got a notice from Microsoft that this SharePoint Online version would be switched over, he said.

"I assume that Microsoft thought no one would be affected," he said.

Eventually, ObjectSharp was able to regain programmatic access to the affected site.

"Microsoft has been so solid, so strong in keeping Office 365 servers up and running, that the idea that this might happen for something so silly as a back-end upgrade and not notify people, I found that simply stunning," Johnson said.

If its customer's site had been live, 20,000 internal users and any external visitors would have lost access to it. The customer has now decided to postpone rolling out this site until Microsoft completes the SharePoint Online move to the 2013 version and all the kinks have been ironed out, he said.

SP Marketplace's Trimble hopes Microsoft gets the situation under control as well.

"This has been a challenge. We're not saying don't go to Office 365. We're just sending a message to Microsoft to get a handle on this. We've got a lot of successful customers out there who love Office 365 and our apps, but they're nervous and it's not because of the platform itself, but because of the way Microsoft is managing it," Trimble said.